CODEWITHSUNDEEP
javaandroidmethodsstatic
marcu
marcu

Reputation: 233

How call getApplicationContext in static method in class who extends Application class?

How to call getApplicationContext in static method in class that extends Application class?

I want to create Database class inside AppContainer class, but I don't know from where get context for Database constructor.

Database

public class Database extends SQLiteOpenHelper {

    public Database(Context context) {
        super(context, "database.db", null, 1);
    }
}

AppContainer

public class AppContainer extends Application{
                                          // Problem---------|
    private static class DatabaseHolder { //                 v
        public static final Database DATABASE = new Database(getApplicationContext()); 
    }

    public static Database getDatabase()
    {
        return DatabaseHolder.DATABASE;
    }
}

==================EDIT

I made error in my code. I forgot write word "static" at getDatabase method. Error has been improved. I don't want to create AppContainer in my code. I want use this class as container with static fields and get them without create AppContainer's instance.

I found solution of my problem:

public class AppContainer extends Application {

private static AppContainer instance;
private static Database database;


public AppContainer() {
    instance = this;
}

public static AppContainer getInstance() {
    if (instance == null)
        synchronized (AppContainer.class) {
            if (instance == null)
                instance = new AppContainer();
        }
    return instance;
}

public static Database getDatabase() {
    if (database == null)
        synchronized (AppContainer.class) {
            if (database == null)
                database = new Database(getInstance().getApplicationContext());
        }
    return database;
}
}

Upvotes: 2

Views: 6966

Answers (3)

Abdul Rahman K
Abdul Rahman K

Reputation: 664

Try creating a static variable of Context type and initialize it in the constructor and hence all that static variable in the method. Like this :

public class AppContainer extends     Application { 
private static AppContainer instance;
private static Context ctx;

private static Database database;
public AppContainer() { 
...

ctx=getApplicationContext();
 } 
...

 public static Database getDatabase()     {
 ....
Database database = new     Database(ctx); 
return database; 
} 

}

Upvotes: 1

matiash
matiash

Reputation: 55380

You probably don't need to initialize the Database object as part of the AppContainer. In particular since your method

public Database getDatabase()
{
    return DatabaseHolder.DATABASE;
}

is not static, it cannot be called unless the Application object is fully initialized. Therefore, you don't need a static reference to it -- having it as a normal instance member, and initializing it in the constructor, should suffice.

public class AppContainer extends Application
{
    private Database mDatabase;

    public AppContainer()
    {
        super();
        mDatabase = new Database(this);
    }

    public Database getDatabase()
    {
        return mDatabase;
    }
}

If, however, you needed to make the getDatabase() method static, then changing the mDatabase instance field into a static field and keeping the rest the same would probably suffice. It's highly unlikely that you would want to access the database before an Application object was available.

Upvotes: 1

betteroutthanin
betteroutthanin

Reputation: 7606

Where will you create the AppContainer object? If you are creating that object in a class which extends to Activity, you can pass the context when creating this object. Basically it looks like this:

public class AppContainer extends Application{
    private Context c;

    public AppContainer(Context context){
        this.c = context;
    }

    .............
}

In the class which extends to Activity:

public class theClass extends Activity{
    AppContainer container = new AppContainer(this);
}

Upvotes: 0

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